INTRODUCTION

Nosocomial infections (NIs) represent a serious public health concern, as they generate high treatment costs, interdict inpatient units and increase the number of deaths.^1,2 It is estimated that between 3% and 15% of hospitalized patients in Brazil develop NIs during their hospital stay³.

No hospital is free from the problem, as there is no intervention available that can eradicate NIs; however, a continuous searching for cases reduction should be one of the main establishment goals. With this aim, the Ministry of Health created specific actions to try to prevent and control NI cases. One of them is developing health policies, which requires the creation of an Infection Control Committee in each hospital. This Committee aims at monitoring NI and controlling the rational use of antimicrobials and germicides¹.

An important aspect that must be considered in NIs is the emergence of multidrug-resistant microbial strains to available antimicrobials, what limit the infections treatment.^4,5 Monitoring the bacteria responsible for NIs and knowing their susceptibility to antimicrobials allows us to locate the infection sources, verify the level of severity to which patients are subject, and devise strategies to alleviate the problem. In this context, this research aimed to trace the profile of microorganisms related to hospital infection and analyze the existence of multidrug-resistance in the Hospital de Caridade de Santo Ângelo/RS, the largest hospital in the city.

METHODS

Study location and samples

This study was carried out at the Hospital de Caridade Santo Ângelo, the largest hospital in the city, with 165 beds, located in northwest Rio Grande do Sul. The Hospital assists 24 cities, covered by the 12^th Regional Health Coordination. The study was retrospective and descriptive, carried out from August 2016 to March 2017. Data were collected from the hospital’s database provided by the Hospital Infection Control Committee, resulting in 100 medical records analyzed. The population consisted of hospitalized patients who developed NI during hospitalization, regardless of age, gender, race, or social status. NI cases were considered to be those isolated from infections that occurred after a patient was admitted to the hospital and that do not appear in the patient’s previous exams.

Microorganisms and susceptibility profile

Microorganism identification and susceptibility profile information were performed by the hospital’s Microbiology Laboratory. Conventional methods of isolation and bacterial identification, involving Gram, growth in selective medium, fermentation of sugars, oxidase, and motility were performed⁶. Of each specimen/sample/site analyzed, only one microorganism was isolated. To determine susceptibility, Kirby-Bauer method (diffusion-on-disk) was used, according to the CLSI standardization (Clinical and Laboratory Standards Institute)⁷. The antimicrobials used were nalidixic acid, amikacin, amoxicillin + clavulanate, ampicillin, ampicillin + sulbactam, azithromycin, aztreonam, cephalothin , cefazolin, cefepime, cefotaxime, cefoxitin, ceftazidime, ceftriaxone, cefuroxime, ciprofloxacin, clarithromycin, clindamycin, chloramphenicol, erythromycin, gentamicin, imipenem, levofloxacin, meropenem, nitrofurantoin, norfloxacin, oxacillin, penicillin, polymyxin, piperacillin + tazobactam, polymyxin, sulfazotrim, and vancomycin.

Identification of multidrug-resistance bacteria, clinical specimen and hospital unit

For multidrug-resistance analysis of the isolates, the concepts established by Magiorakos et al. (2011) were used as reference, in which those isolates resistant to three or more classes of antimicrobials are considered multidrug-resistant.

Moreover, clinical specimen and hospital unit related to NI were identified. Data were tabulated through appropriate coding using Microsoft Excel program.

RESULTS

Analysis of the NI from August/2016 to March/2017 showed the following distribution of cases: August (13%), September (12%), October (12%), November (8%), December (11%), January (13%), February (14%), and March (17%). The 4 most prevalent microorganisms found were Acinetobacter baumannii (17%), Escherichia coli (16%), Staphylococcus aureus (8%), and Pseudomonas aeruginosa (7%), which accounted for a total of 48% cases analyzed. Altogether there were 23 species/groups of bacteria found, plus the yeast Candida albicans (Figure 1).

In relation to NI cases in each hospital unit, we observed that 41% occurred in the adult ICU; 28% in Unit A (surgical patients); 14% in Unit E (patients in general); 11% in Unit B (patients in general); 3% in the newborn ICU (newborns up to 28 days old); 2% in the Pediatric Unit; and 1% in Unit D (maternity). The prevalence of NI microorganisms in the adult ICU was similar to observed in all hospitals, with A. baumannii (21.95%) and E. coli (21.95%) being the most frequent. However, Klebsiella pneumoniae (9.5%) and C. albicans (7.31%) are considered the third and fourth most prevalent, respectively. Meanwhile, P. aeruginosa ranks seven (4.76%) (Figure 1).

Tracheal aspirate (30%), urine (20%), wound secretion (12%), cartilage/sponge/ligament swab (12%), surgical wound (11%), and blood (5%) were the most prevalent clinical sites and specimens providing microorganisms associated with NI. From each site or specimen identified, only one microorganism was isolated.

When we assessed the bacteria in relation to the number of multidrug-resistant antimicrobial classes, we found a large percentage of multidrug-resistant isolates. Sixteen different species/groups of multidrug-resistant bacteria were identified, namely: Morganella morganii (100%), Hafnia alvei (100%), Enterobacter sakazaki (100%), Serratia spp. (100%), Enterobacter aerogenes (100%), Proteusvulgaris (100%), Acinetobacter baumannii (100%), K. pneumoniae (83%), Enterobacter spp. (75%), K. ozaenae (66%), coagulase-negative S. (66%), E. coli (56%), Serratia rubidaea (50%), S. marcensces (50%), S. aureus (37%), and P. aeruginosa (28%).

Bacteria were resistance mainly to amoxicillin + clavulanate, ampicillin, cephalothin, ceftazidime, ceftriaxone, sulfazotrim, and cefepime. For these antimicrobials, all isolates of more than two bacterial species were multidrug-resistant.

DISCUSSION

NIs are challenging in developing countries, occurring at high rates. From August to March, we noticed that March (2017) was the month with the highest rate (17%), while November (2016) was the month with the lowest prevalence (8%). It is difficult to say whether these rates are high or low, as NIs vary according to the hospital size, type of care provided, educational institution, public or private administration, among others. However, experts believe that 1/3 of these infections could be prevented⁹. The highest rate in March was not significantly higher than in other months, with the exception of November, however, it drew attention. More studies would be conducted, in order to verify what was causing this increase in NI rates in this period.

Regarding the microorganisms involved in the infections, we found 23 different bacteria/groups (Figure 1) and one fungus. A. baumannii (17%), E. coli (16%), S. aureus (8%), and P. aeruginosa (7%) appear with a total prevalence of 48%. These bacteria are commonly found also by other researchers as routinely involved in NI. ^2,4,10,11,12

A. baumannii is considered a prominent nosocomial pathogen due to its high resistance to antimicrobials and disinfectants. Despite the most frequent reservoir of this microorganism being infected patients, widespread environmental contamination is frequently observed, appearing on hospital stretchers, even after cleaning process. P. aeruginosa can multiply in soaps and detergents, and these products can often be a source of contamination.^11,13,14

E. coli was the second most evidenced bacterium in the study. Currently, this bacterium has received attention due to increasing cases related to multi-drug resistance, both in hospitals and in the community.^4,15S. aureus, on the other hand, has been considered a nosocomial pathogen that causes high-risk diseases for years. Its infections occur due to colonization of nostrils and skin. This microorganism is characterized by its great capacity to adapt and create mechanisms of resistance to antimicrobials ^5,16, being responsible for almost half of all deaths caused by antibiotic resistant microorganisms.¹²

It is known that patients hospitalized in an Intensive Care Unit (ICU) are critical and are more vulnerable to NI, compared to other inpatients. There are risk factors that increase the susceptibility of these patients, namely: clinical severity; existence of surgeries; use of immunosuppressive and antimicrobial drugs; use of invasive procedures such as central venous catheter and indwelling urinary catheter; use of mechanical ventilators, in addition to intense interaction with the health team; and prolonged hospital stay.^4,14 NI rates in ICU, in general, range between 18 and 54%.¹⁴ Our study showed a rate of 41%, when compared to other hospital wards, indicating that it requires greater care in an attempt to minimize this rate.

The yeast Candida albicans appears as the fourth cause of NI in the ICU. In general, infections caused by Candida, represent 80% of all fungal infections in hospitals, appearing contaminating the bloodstream, urinary tract, and surgical wound. This microorganism is found in the microbiota of the human body, however, it becomes pathogenic when there are changes in the host’s defense mechanisms or in cases of invasive medical procedures. Among 20 the species of Candida, C. albicans has the greatest clinical importance due to its gravity and frequency. ¹⁷

Lung has been highlighted as an important NI site, especially in ICUs. This fact is due to the necessity of patients to stay in bed, frequent use of sedation and multiple invasive procedures of the airways.^4,11,18 Of the 100 medical records analyzed, the sample with the highest microbial isolation found was tracheal secretion/aspirate, with 30% of the total number of cases, in agreement with other research in the field.

The second more prevalent site/clinical specimen found in this study, with 20% of the cases, was the urine. Urinary tract infections can account for up to 35% of all hospital-acquired infections, due to the fact that many hospitalized patients are temporarily exposed to indwelling bladder catheterization.^18,19

It is also necessary to emphasize that the most severe post-surgical cases are usually directed to ICUs. In these cases, E. coli and Klebsiella spp are among the bacteria generally involved in these infections.^2,15 In the present study, 11% of the isolates were from surgical wound exudate and 2% from non-operative, being E. coli and P. aeruginosa the most prevalent bacteria found. Furthermore, of the 11 cases found in the study, five cases were in the adult ICU; and three, two and one case in Unit E, Unit A and Unit D, respectively.

There is a large proportion of bacteria worldwide resistant to at least one antimicrobial, which is generally used in patient therapy. Patients infected by resistant pathogens have longer hospital stay and require treatment with second and third generation medication, which are more toxic and more expensive, generating higher costs for public health.^2,4,5,9

Multidrug-resistance in members of the family Enterobaceriaceae has increased vastly lately. Carbapenemase production is more frequent in enterobacteria of the genus Klebsiella, Enterobacter, Escherichia, Serratia, Citrobacter, Salmonella, Proteus, and Morganella. Carbapenemase attributes resistance to beta-lactam agents such as penicillin, cephalosporins, monobactams, aztreonam, and carbapenems – imipenem. The latter is considered a broad-spectrum drug used in cases of infections caused by multidrug-resistant bacteria.²⁰ In the present study, two isolates of the genus Serratia showed resistance to imipenem, followed by one isolate of E. coli and another of Enterobacter. All isolates came from different sites, such as tracheal aspirate, femur fragment, blood culture, and surgical wound.

Of the 23 species/groups of bacteria found involved in NI, 16 were multidrug-resistant, with resistance to three or more classes of antimicrobials, which confirms that the hospital can be the focus of a large number of different types of bacterial resistance. This multidrug-resistance encumbers treatment, increasing mortality and morbidity rates, in addition to increasing hospital costs.^2,21 The selective pressure exerted by the use of various antimicrobials in an attempt to treat the infection, allowing the emergence of new multidrug-resistant bacteria, becoming a dependent cycle. From the hospital, multidrug-resistant microorganisms are taken to the external environment by employees, patients, and visitors. In the community, these microorganisms spread and reach susceptible individuals, increasing mortality, morbidity, and health expenses outside the hospital, confirming that they are a serious public health concern. ²¹

Data collected in this study prove the need for measures and strategies to avoid cross-contamination and spread of multidrug-resistant bacteria inside and to outside the hospital.

Acknowledgments

We would like to thank the Hospital Santo Ângelo’s Infection Control Committee for providing information, which made this work possible.

REFERENCES

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